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Louisville MSD using bathroom tile to test water quality

Beargrass Creek in Louisville, KY
Beargrass Creek is one of the 27 locations MSD places tiles for algae testing.

The Louisville Metropolitan Sewer District is pulling ceramic bathroom tiles covered in algae from the bottom of local creeks to test the city’s water quality.

While testing the quality of Louisville’s water, MSD found a new use for a common floor material: ceramic tile.

For the last 10 years, the sewer company placed squares of the commonly-used bathroom tile in 27 local creeks. Officials leave them there for 14 days, giving them time to accumulate algae. The algae is then scraped off the tile and sent to a lab for testing.

Colette Easter is the program administrator for the Municipal Separate Storm Sewer System, known as MS4. She said MSD uses the results from algae testing to maintain Louisville’s water quality and balance the local ecosystem.

“We also know more about how we can improve the water, and so working together with the community, as well as our subject matter experts to not only change our behavior, but also change our infrastructure to make sure that we can protect it for generations to come.”

If algae appears on the tiles, Easter said this indicates creeks and rivers can sustain an ecosystem for fish and macroinvertebrates like snails, worms and crayfish.

The local creeks are a part of the city’s water supply, and Easter said these waterways can also become polluted. Some of this can be attributed to human activity affecting natural stormwater, specifically not picking up after dogs, littering near the waterways and laying lawn fertilizers in wet areas.

“Every raindrop that falls, falls on top of our roof and down our gutters and along the street.” Easter said, “And along the way before it gets into our pipes and drainage systems, it can pick up salts and oils and grease and other nonpoint source pollution that we are trying to manage and maintain. And then it, in the end, deposits into our creeks, and then also … ends up in the Ohio River.”

Easter encourages Kentuckians to work with MSD to protect aquatic life and the future of the city’s water quality by taking steps to limit this pollution.

She explained the condition of Louisville’s creeks and streams “didn’t happen overnight.”

MSD has worked with algae tile testing for the last 10 years as part of the MS4 permit, under the Clean Water Act. The permit also allows MSD to deposit natural stormwater into local lakes, rivers and streams.

The results will be recorded in MSD’s State of Streams report in 2026.

Giselle is LPM's breaking news reporter. Email Giselle at grhoden@lpm.org.

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